As Greg once stated me "to be dedicated for the very least", when I wrote about the ANBO VIII, here is about another little one. Small in dimensions, and small in success. Nevertheless, it incorporates one of the biggest flops in German aircraft development history of WWII, which is really not very poor of numbers.

Big failures often result from big ideas. In our case, what I mean is the so-called Z-Plan. This was a plan for a giant German naval armament program, to bring the country on eye level with the leading naval powers USA and Great Britain. The plan also included to build a number of very big submarines, labeled as "class No. XI".

Four ships were planned to be built: U-112, U-113, U-114 and U-115. These were laid out as subcruisers of 2.659 tons displacement of water, carrying 4 6-inch cannons each and - a boardplane. For to store this, a cylindric tube of 7,5 x 2,25 m was foreseen.

Although Heinkel had already experience with submarine boardplanes, the order to develop one, without any noticed competition process, went to Arado. Middle of 1938, the firm started the drafting and calculation works. When WWII began, the prelimimary task was done, and the first prototype could be constructed. However, one of the first "victims" of WWII was - the Z-Plan. Although it was forseeable that sooner or later a strategic conflict between Germany and the USA would arise, which would require a big fleet of all thinkable kinds of ships, the plan was cancelled - for tanks, gun-barrels, engines and steel helmets, which were considered the more urgent need to make use of the steel production. But although there would be no mothership, the development of the Ar 231 continued.

The little airplane was laid out as single-crew single-engined strutted parasol high-wing with double floats. The center-wing section had a charateristic incline of 11,5 degrees and was fixed to the fuselage (see picture #1). The incline was to accomodate the folding of the wings, in which the left one became laying over the right one. Also, the struts of the floats could be folded and thus making the floats to lay in a position close to the fuselage (see pictures #4 and 5). The mother submarine needed a special crane for to take the aircraft aboard, also a slay for to move the aircraft in and out the storage tube, where it was also stored together with the airplane. The storage was done nose-down for to prevent pollution by leaking oil.

The fuselage cover was made of "hydronalium", surely a special salt-water resistant alloy. For to drive the aircraft, a Hith HM 501 air-cooled inline engine of 160 hp was installed. It was planned that, in case of the mother submarine had to do emergency diving while the aircraft was on sortie, to keep the aircraft in the air cruising for 6 hours with a throttled-down engine at a speed of only 38 kph, waiting and hoping the mothership would appear on the surface once again. Folding and unfolding of the aircraft should have been done within just 10 minutes.

The aircraft made its first flight on 25 July 1940. Until May 1941, four samples were transferred to the seaplane test center at Travemünde near Lübeck. There, until September 1941 numerous tests were performed, most of them successfull after various initial troubles. However, U-boat commanders, asked on their opinion about the project, proved to be sceptical. 10 minutes or not, any fact that delays the diving capability of a submarine would not be pleasing the sub's commander. And once detected, the presence of an aircraft like this makes the opponent necessarily conclude to the presence of the mothership.

Furthermore, when it was found out that the aircraft could not be salvaged by the mother boat at a wind force of Beaufort 6 without collision, the whole project was stopped (personal remark: If you read the definition of "Beaufort 6", it is pretty much for seaplane action. Here, in my eyes, the requirements might be exaggerated, RT). Submarine boardplane task was placed on the bound and towed motorless helicopter Focke-Achgelis FA 330 (a device not less unpopular among U-boat commanders, as it could be spotted the same way easy as a free and self-driven boardplane, thus revealing the mother boat, that had to cut the hawser and abandon machine and pilot for emergency diving, without herself having a guarantee for to escape).

On this point, the story of the Ar 231 could calmly finish. But fate did not foresee this and chose a dramatical ending, when two remaining Ar 231s, V 3 and V 4, were detached to become boardplanes of German auxiliary cruiser (aka merchant raider) Stier (means "bull" in English, see picture #6).

On 19 May 1942, Stier left the French harbour fortress of Royan for South Africa. During the journey, on which Stier managed to sink three Allied merchant ships, various efforts were done to bring the two Arados into the air. But the aircraft proved completely unsuitable for the task. Stier, like any other German auxiliary cruiser, lacked a catapult, and the Ar 231s could not take off even from the calmest seas. It took until 23 August 1942 when Stier was already cruising in the Southern Atlantic, with all equipment removed and fuel tank only filled to a quarter, that one Arado managed to take off, thus creating one of the shortest operational careers of WWII warplanes.

On 27 September, Stier had a rendezvous with blockade runner Tannenfels, coming from Japan, when an alien ship came into sight, and Stier ordered it to stop. The other one happened to be armoured US Liberty ship Stephen Hopkins. In the following fierce artillery duel, both ships received fatal hits. While Stier's crew had exceptional luck becoming picked up by Tannenfels, that safely arrived at Bordeaux on 8 November, the few survivors of Stephen Hopkins reached the Brazilian coast on 29 October. Together with Stier, the two Arado boardplanes sank to their dark and wet grave in the Atlantic ocean.

One of the authors of my sources, Kranzhoff, states that the failure of the Ar 231 could easily have been predicted and complains that 85.000 hours of designing and 25.000 to 30.000 hours of constructing for every sample were lost. A harsh number if you consider Neitzel quoting Willy Messerschmitt telling Hitler that the Me 264, an airplane of uncomparably bigger glamour and meaning, needed 75.000 hours to be completed in design, an amount that also Hitler couldn't deliver...

Pictures:

#1: The drawing from aviarussian.ee shows the characteristic incline of the centerwing section:

Obscure though it may be, I concur that it was a waste. It was probably a pretty good little airplane with no real wartime use. If reintroduced today in landplane form, it might very well be embraced by the light aircraft comminuty since it folds up nicely to be trailered home from the flying field, but it would have to saet another person to be viable.

For wartime use, a 160hp, single-place, folding aircraft is just not much of an offensive weapon, and cannot even defend itself in the event of attack from an advanced trainer. So, the resulting uselessness could easily have been predicted before expending the effort to build it, given a modicum of forethought and consulting several U-Boat commanders.

It might well be useful as a scout for a capital ship. If spotted and if the mother ship were to be located, it might very well be at the expense of the attacking force. However, a big capital ship doesn't need a folding aircraft, so they wouldn't want to spend the useless 10 minutes either.

Obscure though it may be, I concur that it was a waste. It was probably a pretty good little airplane with no real wartime use. If reintroduced today in landplane form, it might very well be embraced by the light aircraft comminuty since it folds up nicely to be trailered home from the flying field, but it would have to saet another person to be viable.

What did they do to the prop during storage? The prop's diameter apparently is LARGER than the diameter of the aircraft's storage-tube?

I don't think so, Michael. By the rails of the slay you see that the aircraft is protruding halfway out of the tube. From this camera position, proportions easily get contorted. I think the airscrew fits perfectly into the tube!

quote:Montanamotor wrote:

In his autobiography "Mein stürmisches Leben" there are some pics of his Caspar-Heinkel U1 - which he sold in several examples to the USA AND Japan, alike.

That's what I was talking about when I said Heinkel had corresponding experience!

quote:Montanamotor wrote:

Errr - building a submergible aircraft-carrier makes about as much sense as: Putting BIG guns in a submarine...? Errr...

When I asked a corresponding question in the Battleship Bismarck Forum, I was told that in the beginning of the war submarines often did their job using their cannons - not that I didn't know that, but contributors who answered me gave remarkable credit to the, only example, artillery of the French Surcouf. At least you can use it for to demolish remote harbours at night, maybe after you have reconnoitered them by your boardplane in daylight before...

quote:GregP wrote:

it might very well be embraced by the light aircraft comminuty since it folds up nicely to be trailered home from the flying field

Let's have some business, Greg! You know there are commercial submarines, I think there is one diving around in Pearl Harbour for underwater sightseeing. We don't need to revive the old Ar 231 (as long as Montanamotor doesn't build a replicate... ), we take the Floatflea instead:

We combine a commercial submarine with a little hangar for the Floatflea and have an unique diving yacht!

Obscure though it may be, I concur that it was a waste. It was probably a pretty good little airplane with no real wartime use.

It's easy to forget that at the time was it essential to reconnoitre by eyes.
For every two meters one rises, the distance of sight extends with one kilometre, and the Arado would have done the job of being the eyes in the sky pretty well If it wasn't because of it's bad qualities in the air!

I saw that it had a hard time flying, Wuzak, but I think with more modern airfoil and possibly a 180 - 200 HP engine, and without the weight and drag of the floats, it might make a light sport aircraft that could be trailered to the airport.

But it's still ugly enough to stop a donkey and make him swoon. Maybe if they painted it pink?